The present disclosure relates to an image forming apparatus and an image forming method for forming a color image.
There is generally known an image forming apparatus such as a printer that can form a color image by the electrophotography. In this type of image forming apparatus, a color image is formed, for example, through a procedure in which a plurality of toner images of different colors formed on image carriers such as photoconductor drums are transferred in such a way as to be overlaid in sequence on the intermediate transfer belt, and then the toner images of different colors overlaid on the intermediate transfer belt are transferred on a transfer target member such as a sheet.
Meanwhile, in this type of image forming apparatus, when a character image is printed, a phenomenon called void of image may occur, in which a part of the toner images formed on the image carriers is not transferred to the intermediate transfer belt, and a hole is made in the toner image on the intermediate transfer belt. It is known that the void of image occurs when the toner aggregates in transfer nip portions due to stress concentration, wherein the transfer nip portions are formed by the image carriers, the intermediate transfer belt, and transfer rollers for transferring the toner images to the intermediate transfer belt. As a technology related to this problem, there is known an image forming apparatus that can restrict the occurrence of the void of image by reducing the contact pressure applied to the intermediate transfer belt, wherein the contact pressure to be reduced may be the contact pressure applied to the intermediate transfer belt from all the transfer rollers or the contact pressure applied only from a transfer roller for transferring a black toner image.